In recent years, according to improvements in image quality from VGA (Video Graphics Array) to XGA (eXtended Graphics Array) in flat-panel displays represented by LCD television sets and plasma television sets, signal speed for transferring image information is increasing. Accordingly, as a system for use in high-speed digital data transmissions, a further differential transmission system of low amplitude has been used. The transmission system is provided for transmitting signals having mutually opposite phases and equal amplitudes via two wiring patterns formed on one balanced cable or a printed wiring board. The system has the features of low noise, strong resistance to external noises, low voltage amplitude, high-speed data transmission and so on, and has been introduced as a high-speed transmitting method particularly in the field of displays.
However, in the actual differential transmission for transmitting a transmission signal from a signal transmitter apparatus to a signal receiver apparatus via a differential transmission path constituted to include one pair of transmission lines, a cross point between signals inputted to the signal receiver apparatus has been shifted by variations in the characteristics of the differential driver amplifier that constitutes the signal transmitter apparatus and the loss of symmetry of the differential transmission path, and the transmission signal could not be accurately transmitted.
In a pulse width correction circuit according to the prior art described in the Patent Document 1, the cross point between differential signals is set to an appropriate point by connecting variable capacitance means and a bias power source to each differential transmission path and adjusting the output phase shift of the differential signal transmission line with the capacitance of the variable capacitance means changed by adjusting the voltage of the bias power source.    Patent Document 1: Japanese patent laid-open publication No. JP-11-225172-A